I use Liquifile from time to time to identify those places in the file system that have grown a little bloated over time, and to see if I can thin things out anywhere. It gives a unique visual interface into your entire directory structure, allowing you to easily see where all the space is being used, and how long it's been used for.

I used it yesterday in just such an exercise and discovered a hitherto unknown feature of another piece of software I've been using, namely OSXPlanet. OSXPlanet creates almost 'live' views of planet Earth on your desktop, including such things as clouds, satellites and volcano eruptions.

What I didn't know, however, was that it seems to keep a cache of every desktop picture it has generated, which, if you have the refresh rate set particularly high, can result in numerous redundant images being created.

I can see where some people may find this useful -- indeed I've managed to use QuickTime to combine the images into movies of daily events on Earth, so I wouldn't want to see the feature squashed. However, I did manage to accrue 34,000 of these images, equaling nearly 60Gb of data, which is now free space again thanks to Liquifile.

[robg adds: There are any number of disk space tools out there; which one you use is really a matter of personal preference. I don't like the visual usage tools -- my mind much prefers things that look like spreadsheets, so I use Omni's free OmniDiskSweeper, which runs great in 10.6. Other possibilities include: Disk Inventory X (free), GrandPerspective (free), jDiskReport (free), WhatSize ($13), and DaisyDisk ($20). I'm sure I've missed some; if you have a favorite, post it in the comments.]

If you feel comfortable with lists, just use the finder in column view and switch on "always calculate size" in view options. I added the size as a column and sort after it. No extra software needed :)

I do consider this as a bug in OSXplanet; my expectation is that if I switch "Archive the Images created for this screen" either off or set a limit (like 1), this issue doesn't appear.

BTW, you can also just delete the contents of the folder /Users/<put_your_short_username_here>/Library/Application\ Support/OSXplanet/desktop/screen\ 0/ and repeat it for all screen 1,...,n you have in addition...

I too was wondering where all my disc space was going. To my surprise, OSXPlanet had 21,000 images in this folder....at 2mb per image. I've been using OSXPlanet for years, and don't recall this being an issue. My oldest image in the folder was from 11/2009. Might have been when I updated last.